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|Trade names||Noristerat, Norigest, others|
|Synonyms||NETE; NET-EN; Norethindrone enanthate; SH-393; 17α-Ethynyl-19-nortestosterone 17β-enanthate; 17α-Ethynylestra-4-en-17β-ol-3-one 17β-enanthate|
|AHFS/Drugs.com||International Drug Names|
|Drug class||Progestin, progestogen, progestogen ester|
|Chemical and physical data|
|Molar mass||410.598 g/mol|
|3D model (JSmol)|
Norethisterone enanthate (NETE), also known as norethindrone enanthate, is a form of progestogen-only injectable birth control. It may be used following childbirth, miscarriage, or abortion. The failure rate per year in preventing pregnancy is 2 per 100 women. Each dose lasts two months with up to two doses recommended.
Side effects include breast pain, headaches, depression, irregular menstrual periods, and pain at the site of injection. Use in those with liver disease is not recommended as is use during pregnancy due to risk of birth defects. Use appears to be okay during breastfeeding. It does not protect against sexually transmitted infections. NETE is an ester and prodrug of norethisterone, through which it works. It works as a method of birth control by stopping ovulation.
Norethisterone was patented in 1951 and came into medical use in 1957. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about 1.04 to 7.99 USD per 200 mg vial. It has been approved in more than 60 countries including the United Kingdom and some in Europe, Central America, and Africa. It is not available in the United States.
Side effects of NETE may include breast pain, headaches, depression, irregular menstrual periods, and pain at the site of injection. It can cause birth defects in the fetus if used during pregnancy.
NETE is a prodrug of norethisterone in the body. Upon reaching circulation, it is rapidly converted into norethisterone by esterases. Hence, as a prodrug of norethisterone, NETE has essentially the same effects as norethisterone, acting as a potent progestogen with additional weak androgenic and estrogenic activity (the latter via its metabolite ethinylestradiol).
Similarly to oral norethisterone and norethisterone acetate, intramuscular NETE has been found to form ethinylestradiol as an active metabolite. With a single intramuscular injection of 200 mg NETE in premenopausal women, the mean maximum concentration of ethinylestradiol was 32% of that of a combined oral contraceptive containing 30 μg ethinylestradiol, the maximum equivalent oral dose of ethinylestradiol observed in the first few days of exposure was 20.3 μg/day, and the mean equivalent oral dose of ethinylestradiol over 8 weeks was 4.41 μg/day. As such, the exposure to ethinylestradiol was described as markedly lower than that of an oral contraceptive containing 30 μg ethinylestradiol. The estimated conversion rate of NETE into ethinylestradiol was 0.1%, which was much lower than that observed for oral norethisterone and norethisterone enanthate (0.2–1.0%), likely due to the lack of the first-pass through the liver with parenteral administration. In accordance with the low levels of ethinylestradiol produced, no increase rates of thromboembolism or hepatic adenoma have been observed in post-authorization data of intramuscular NETE, and the medication does not resemble combined oral contraceptives containing ethinylestradiol in its safety profile.
NETE, also known as norethinyltestosterone enanthate, as well as 17α-ethynyl-19-nortestosterone 17β-enanthate or 17α-ethynylestra-4-en-17β-ol-3-one 17β-enanthate, is a progestin, or synthetic progestogen, of the 19-nortestosterone group, and a synthetic estrane steroid. It is the C17β enanthate ester of norethisterone. NETE is a derivative of testosterone with an ethynyl group at the C17α position, the methyl group at the C19 position removed, and an enanthate ester attached at the C17β position. In addition to testosterone, it is a combined derivative of nandrolone (19-nortestosterone) and ethisterone (17α-ethynyltestosterone). Esters related to NETE include norethisterone acetate and levonorgestrel butanoate.
Norethisterone and its acetate and enanthate esters are progestogens that have weak estrogenic and androgenic properties.